Paramagnetic molecules including oxygen, oxygen radicals and nitric oxide modulate cellular function and injury, altering critical cellular processs such as respiration and redox state with changes in tissue perfusion, energetic state and viability. In view of the critical importance of these interactions in normal cardiovascular functin and disease, there has been a great need for an approach to combine in vivo measurement and imaging of paramagnetic molecules with imaging of tissue and organ biochemical and functional parameters in animal models of disease. EPR imaging (EPRI) is a powerful technique that enables 3D spatial in vivo mapping of radical metabolism, oxygenation, and nitric oxide; however, the utility and power of EPRI has been greatly limited by the need for complementary anatomic and functional data. NMR based MRI, in addition to providing anatomic registration, also can provide critical functional information that is needed to interpret the EPRI data including, imaging of tissue perfusion and viability. Integrated EPR/NMR imaging technology and instrumentation has the unique potential to enable in vivo mapping of free radicals, oxygen and nitric oxide along with NMR based functional and anatomic imaging. This technology is very promising but several fundamental problems presently limit its development and biomedical application. These include the need to: [a] provide seamless integration of the EPR and NMR-MRI systems to enable rapid transition between these two imaging modalities; [b] build dual mode resonators optimized for both EPR and NMR resonances suited for specific biomedical applications; [c] accelerate the process of image data collection in both modes facilitating dual mode anatomic and functional imaging; [d] increase sensitivity and minimize motion-induced noise or image distortion; [e] integrate the EPRI and MRI results and analysis in order to perform accurate image co-registration, fast computation and interpretation of functional data. These critical needs will be addressed with a combination of hardware and software development followed by testing in cardiovascular applications as described in 3 specific aims: I. Development and construction of EPRI hardware optimized for high sensitivity fast scan image acquisition and integration of it with high field MRI; II. Development / implementation of integrated software and algorithms for fast EPRI and NMR MRI acquisition with cardiac gating enabling co-mapping of anatomic structure, perfusion, energetic state and viability (MRI) with free radical distribution, redox state and oximetry (EPRI). EPRI acquisition will be accelerated and refined using NMR image information to refine EPR data collection; III. Application for dual mode functional imaging of the heart with both in vivo and ex vivo measurement of tissue O2 levels, redox status, nitric oxide formation (EPRI) in relation to perfusion, viability, and energeic state (MRI). This program will realize the great synergy and power of integrated real time EPRI and high field MRI optimized for biomedical measurement and imaging of free radicals, redox state, O2, and nitric oxide and their role in function and disease.